Figure 2.12 Configuration options for the NUMA configuration of a virtual machine
Consider a large Hyper-V environment with many types of servers. The physical
servers have different NUMA topologies, and virtual machines may be live-migrated
between the servers. In this case, the NUMA configuration should be changed to
match the smallest NUMA topology among all of the servers to which the virtual
machine may be migrated. For example, suppose I have two servers:
Server 1 NUMA topology: Maximum number of processors is 16, and maximum
amount of memory is 63822.
Server 2 NUMA topology: Maximum number of processors is 8, and maximum
amount of memory is 22720.If a virtual machine is created on Server 1, that is the NUMA topology that will be
configured for the virtual machine. If the virtual machine is then moved to Server 2,
the VM will have incorrect NUMA configuration and will not have optimal resource
assignments, because what it believes is a single NUMA node actually spans multiple
NUMA boundaries. It therefore makes sense to set the NUMA topology of the virtual
machine manually to match that of Server 2. Hopefully in the future, the management
solutions for Hyper-V will look at all of the nodes in a cluster and automatically
configure virtual machines with a NUMA topology that matches the smallest NUMA
configuration in the cluster. At the time of this writing, this does not occur.